Generally, fine pattern formation is carried out by the photolithography in manufacturing processes of a semiconductor device. A number of substrates called transfer masks (photomasks) are normally used for this fine pattern formation. The transfer mask comprises generally a transparent glass substrate having thereon a fine pattern made of a metal thin film or the like. The photolithography is used also in the manufacture of the transfer mask.
In the manufacture of a transfer mask by the photolithography, use is made of a mask blank having a thin film (e.g. a light-shielding film or the like) for forming a transfer pattern (mask pattern) on a transparent substrate such as a glass substrate. The manufacture of the transfer mask using the mask blank comprises an exposure process of applying required pattern writing to a resist film formed on the mask blank, a developing process of developing the resist film according to the required pattern writing to form a resist pattern, an etching process of etching the thin film according to the resist pattern, and a process of stripping and removing the remaining resist pattern. In the developing process, a developer is supplied after applying the required pattern writing to the resist film formed on the mask blank to dissolve a portion of the resist film soluble in the developer, thereby forming the resist pattern. In the etching process, using this resist pattern as a mask, an exposed portion of the thin film, where the resist pattern is not formed, is dissolved by dry etching or wet etching, thereby forming a required mask pattern on the transparent substrate. In this manner, the transfer mask is produced.
For miniaturization of a pattern of a semiconductor device, it is necessary to shorten the wavelength of an exposure light source for use in the photolithography in addition to the miniaturization of the mask pattern formed in the transfer mask. In recent years, the wavelength of an exposure light source in the manufacture of a semiconductor device has been shortened from a KrF excimer laser (wavelength 248 nm) to an ArF excimer laser (wavelength 193 nm).
As a type of transfer mask, apart from a conventional binary mask having a light-shielding film pattern made of a chromium-based material on a transparent substrate, there has appeared in recent years a binary mask or the like using, as a light-shielding film, a material such as MoSiN containing a transition metal and silicon as main metal components and further containing nitrogen, as described in Patent Document 1.
In the meantime, hitherto, with respect to a transfer mask manufactured from a mask blank by forming a transfer pattern in a light-shielding film by dry etching using as a mask a resist pattern formed in a resist film by electron beam writing and development or an etching mask pattern formed in an etching mask film, a comparison is made, using a pattern inspection apparatus, between a design transfer pattern and the transfer pattern formed in the light-shielding film and a defect (so-called black defect) portion where the light-shielding film remains in excess as compared with the design transfer pattern is corrected by a physical treatment using nanomachining or focused ion beam FIB (Focused Ion Beam). However, there has been a problem that the black defect correction by such a physical treatment takes much time. Further, since the irradiation dose of Ga ions becomes large in the normal FIB treatment, Ga stain remaining on a QZ substrate has been a problem. In view of this, there has been reported a technique of gas assist or the like for enhancing the reactivity to suppress the Ga irradiation dose (see Patent Document 2).
On the other hand, Patent Document 3 discloses a defect correction technique that supplies a xenon difluoride (XeF2) gas to a black defect portion of a light-shielding film and further irradiates an electron beam onto the black defect portion, thereby etching the black defect portion to remove it (hereinafter, such defect correction that is carried out by irradiating charged particles such as an electron beam will be referred to simply as EB defect correction). Such EB defect correction was at first used for correction of a black defect portion in an absorber film of a reflective mask for EUV lithography, but has started to be used also for defect correction of a MoSi-based halftone mask.